Feature/metaindexer torrent download improvement (#1517)

* Line endings...

* Improve download handling of torrents in metas

Until now, downloads were handled by metas, however they had to "guess"
which indexer the result was originating from and resolve to that
indexer. While this has been working without an issue, it really
shouldn't be considered stable.

Therefore indexers now link themselves to the results they provide. In
order to keep my sanity and automate this as much as possible, I had to
slightly modify the interface (sorry, everyone).

src/Jackett/Indexers/Norbits.cs

@@ -222,7 +222,7 @@ namespace Jackett.Indexers
         /// </summary>
         /// <param name="query">Query</param>
         /// <returns>Releases</returns>
-        public override async Task<IEnumerable<ReleaseInfo>> PerformQuery(TorznabQuery query)
+        protected override async Task<IEnumerable<ReleaseInfo>> PerformQuery(TorznabQuery query)
         {
             var releases = new List<ReleaseInfo>();
             var torrentRowList = new List<CQ>();